Elicitors In Fungal Metabolites On Improvement Of Natamycin

Natamycin is antibiotic which is an efficient, broad-spectrum antifungal antibiotic by fermentation of Streptomycin natalensis,Streptomyces chatanoogensis and Streptomyces gilvosporeus. Because of its low level fermentation and high cost and in order to increase the fermentation level of natamycin, studying the related rule and using it to guide and improve fermentation process might be of great importance.The concept of elicitor derived from the factors which induce phytoalexin production and allergic reaction in the physiological process of plant disease resistance, and it can highly induce the expression of specific genes under the interaction of plants and microbes. In this paper, the following five areas on fungal elicitor on metabolism of Streptomyces natalensis were studied:1. The exploration on the inducing effect of co-cultivation of immobilized cells. The researches were focused on the inoculative time of immobilized S. cerevisiae, the inoculum volume, the amount of entrapped cells, and how about these kinds of factors might make influences on the co-cultivation system. The results showed that the immobilized co-culture method can not effectively induce the synthesis of natamycin, and Saccharomyces cerevisiae is not a very effective biological elicitor which only increased the yield of natamycin production by 10%. The elicitor is possible components of yeast cell.2. Elicitors screening. Saccharomyces cerevisiae, Aspergillus oryzae, Aspergillus niger and Penicillium chrysogenum as the inducing strains were studied on the promotion of natamycin production. The results showed that metabolites derived from different fungi and different preparation methods had different impacts on yield of natamycin. The up-regulation of elicitors prepared from Aspergillus niger and Penicillium chrysogenum was effective. When 5% elicitors were added into the medium in which Streptomyces natalensis was grown for 12 h, the yield of natamycin in culture broth reached to 209.1% and 262.8% comparing with the control.3. Optimization of induction conditions. The culture time of Penicillium chrysogenum as elicitor, the adding time from the start of Streptomyces natalensis cultivation and the addition amount of elicitor from Penicillium chrysogenum were studied for the effect on the synthesis of natamycin. The results showed that the different culture time of Penicillium chrysogenum and adding time for elicitor have a significant difference on induction. The elicitor cultured 1 d or 2 d with adding time 12 h could promote the synthesis of natamycin significantly. When the adding time delayed, the effect of induction is decreased. Elicitor addition on induction of natamycin showed an insignificant effect.4. Preliminary study of induction mechanism. The physiological and biochemical indexes were measured at the end of fermentation. The results showed that fungal elicitor can improve the utilization of reducing sugar in the medium and inhibit the cell growth. Elicitor can not significantly change the colonial morphology in solid medium, but inhibit the growth of Streptomyces natalensis and promote conidia germination obviously.5. Elicitor separation and identification. Various components were obtained from the non-cell filtration of Penicillium chrysogenum culture broth by ethanol precipitation and used to check the inducing ability for the production of natamycin. The result showed that the elicitor is small molecule neither protein nor polysaccharides. The active supernatant was extracted with organic solvents and used for inducing test. The result that active part mainly in the water phase showed the elicitor might be polar small molecule. By comparing the metabolic pathways of Streptomycin natalensis with Penicillium chrysogenum, elicitor might be organic acid or amino acid.